In the gas supplying apparatus for semiconductor manufacturing equipment, conventionally, a thermal type flow control system and a pressure type flow control system are widely used.
FIG. 5 shows a pressure type flow control system used in a gas supplying apparatus for semiconductor manufacturing equipment, and this pressure type flow control system FCS includes a control valve CV, a temperature detector T, a pressure detector P, an orifice OL, and an arithmetic and control unit CD, etc., and the arithmetic and control unit CD includes a temperature correction/flow rate arithmetic circuit CDa, a comparison circuit CDb, an input-output circuit CDc, and an output circuit CDd, etc.
In this pressure type flow control system, detection values from the pressure detector P and the temperature detector T are converted into digital signals and input into the temperature correction/flow rate arithmetic circuit CDa. Thereafter, temperature correction of the detected pressure and flow rate computation are performed, and, then, a computed flow rate value Qt is input into the comparison circuit CDb.
On the other hand, a set flow rate signal Qs is input from the terminal In, converted into a digital value in the input-output circuit CDc, and then input into the comparison circuit CDb. Qs is then compared with the computed flow rate value Qt from the temperature correction/flow rate arithmetic circuit CDa. When the computed flow rate value Qt is larger than the flow rate setting signal Qs, a control signal Pd is output to the drive unit of the control valve CV, and the control valve CV is driven in a closing direction via a drive mechanism CVa. That is, the control valve is driven in the valve closing direction until the difference (Qt−Qs) between the computed flow rate value Qt and the flow rate setting signal Qs becomes zero.
The pressure type flow control system FCS itself is known, and has excellent characteristics in which, between the downstream side pressure P2 of the orifice OL (that is, the pressure P2 on the process chamber side) and the upstream side pressure P1 of the orifice OL (that is, the pressure P1 on the outlet side of the control valve CV), when the relationship of P1/P2≥approximately 2 (so-called critical expansion condition) is held, the flow rate Q of the gas Go distributed through the orifice OL satisfies Q=KP1 (here, K is a constant). By controlling the pressure P1, the flow rate Q can be controlled with high accuracy, and even if the pressure of the gas Go on the upstream side of the control valve CV greatly changes, the control flow rate value hardly changes.
Thus, in the gas supply equipment for semiconductor manufacturing equipment of a type that divides and supplies a gas to one or a plurality of process chambers, as shown in FIG. 6 and FIG. 7, for respective supply lines GL1, GL2, pressure type flow control systems FCS1, FCS2 are provided, respectively, and, accordingly, the gas flow rates Q1, Q2 of the respective supply lines GL1, GL2 are regulated.
Therefore, the pressure type flow control system has to be installed for each divided flow passage of process gas. This creates the basic problem that downsizing and reductions in the cost of the gas supplying apparatus for semiconductor manufacturing equipment are difficult.
In FIG. 6, the reference symbol S denotes a gas supply source, G denotes a process gas, C denotes a chamber, D denotes a two-divided gas discharging device, H denotes a wafer, I denotes a wafer holding base (Japanese Published Unexamined Patent Application No. 2008-009554), and in FIG. 7, the reference symbol RG denotes a pressure regulator, MFM1, MFM2 denote thermal type flow meters, P2A, P2B, P1 denote pressure gauges, V1, V2, V3, V4, VV1, VV2 denote valves, and VP1, VP2 denote exhaust pumps (Japanese Published Unexamined Patent Application No. 2000-305630).
To solve the problem described above in the gas supplying apparatus shown in FIG. 6 and FIG. 7, as shown in FIG. 8, a divided flow supplying apparatus is developed in which sonic nozzles or orifices SN1, SN2 are interposed in the respective branched gas supply lines GL1, GL2. By holding the primary side pressure P1 of each of the orifices SN1, SN2 to be approximately three times as high as the secondary side pressure P2 of the orifices SN1, SN2 by regulating the automatic pressure controller ACP provided on the gas supply source side by a control unit ACQ, predetermined divided flow rates Q1, Q2 determined according to the hole diameters of the orifices SN1, SN2 are obtained (Japanese Published Unexamined Patent Application No. 2003-323217).
However, in the flow control system (divided flow supplying apparatus) disclosed in Japanese Published Unexamined Patent Application No. 2003-323217 described above, the automatic pressure controller ACP, the control unit ACQ, and the orifices SN1, SN2 are installed individually, and the primary side pressure P1 is held at a value three times as high as the secondary side pressure P2 to make the flow rates Q1, Q2 proportional to the primary side pressure P1, and the gas flows that are distributed through the orifices SN1, SN2 are made as flows in the critical states.
As a result, it is necessary to appropriately assemble and integrate the automatic pressure controller ACP, the control unit ACQ, and the orifices SN1, SN2, etc., so that manufacturing of the gas supplying apparatus becomes troublesome. In addition, it is difficult to downsize and compactify the gas supplying apparatus.
Furthermore, the control system of the control unit ACQ and the automatic pressure controller ACP does not adopt so-called feedback control. As a result, it becomes difficult for the automatic pressure controller ACP to swiftly adjust the fluctuation of the primary side pressure P1 caused by opening and closing operations of the opening and closing valves V1, V2. Eventually, the opening and closing operations of the opening and closing valves V1, V2 cause fluctuations of the flow rates Q1, Q2 (or the flow rate Q).
Furthermore, the primary side pressure P1 is regulated by the automatic pressure controller ACP. When the ratio P1/P2 of the primary side pressure P1 to the secondary side pressure P2 of the orifice is held at approximately 3 or more, the divided flow rates Q1, Q2 are controlled, so that when the value of P1/P2 approaches approximately 2 and the gas flow becomes a gas flow under a so-called non-critical expansion condition, accurate divided flow control becomes difficult.